About a month ago I made a starter from half a vial of White Labs WLP002. I used roughly 600 ml of 1.040 starter wort in a 2L flask on a stir plate and estimated the cell count to be just over 100 Billion using YeastCalc. I wound up not brewing that weekend and put the flask in the fridge with tightly sealed foil covering the opening. It's been in the fridge for the past 4 weeks. Any thoughts on how many viable cells it might contain now? The plan is to step it back up in another starter and brew a 2.5 gallon batch in a couple of days. Thanks.